Vertical coaptation zone in a planar portion of prosthetic heart valve leaflet

ABSTRACT

Described embodiments are directed toward prosthetic valve leaflets of a particular shape that allows redundant coaptation height in the leaflets when a planar segment is present in each leaflet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to provisional application Ser. No.61/739,721 filed Dec. 19, 2012, which is herein incorporated byreference in its entirety.

FIELD

The present disclosure relates generally to prosthetic valves and morespecifically, to the geometry of flexible synthetic heart valveleaflets.

BACKGROUND

The durability of synthetic materials used for heart valve leafletsunder the repetitive loads of the opening and closing is dependent, inpart, on the load distribution between the leaflet and the frame.Further, substantial load is encountered on the leaflet when in theclosed position. Mechanical failure of the leaflet can arise, forexample, at the mounting edge, where the flexible leaflet is supportedby the relatively rigid frame. The repetitive loads of leaflet openingand closing leads to material failure by fatigue, creep or othermechanism, depending in part on the leaflet material. Mechanical failureat the mounting edge is especially prevalent with synthetic leaflets.

The durability of the valve leaflets is also a function of the characterof bending by the leaflet during the opening-closing cycle. Small radiusbends, creases and intersecting creases, can produce high stress zonesin the leaflet. These high stress zones can cause the formation of holesand tears under repetitive loading.

Prosthetic valves may be delivered using surgical or transcathetertechniques. A surgical valve is implanted into a patient usingopen-heart surgical techniques. The surgical valve is usuallymanufactured to have a fixed diameter as opposed to a transcathetervalve which is required to attain a range of diameters for access anddelivery. The surgical valve is usually provided with a sewing cuffabout a perimeter of the valve to allow for suturing to the nativetissue orifice.

In addition to the valve durability issues discussed above, thetranscatheter valve must also be able to withstand the handling anddeployment stresses associated with being compressed and expanded

A “preferred” shape of synthetic heart valve leaflets has been describedmany times, but each is different from the others. The various transientthree dimensional shapes range from spherical or cylindrical totruncated conical intersections with spheres, and an “alpharabola”. Theshape most often described as “preferable” is modeled after the nativehuman aortic valve. Though nature dictates the optimum shape for thenative tissues to form a heart valve, we have discovered this is nottrue for synthetic materials.

SUMMARY

Described embodiments are directed to an apparatus, system, and methodsfor valve replacement, such as cardiac valve replacement. Morespecifically, described embodiments are directed toward flexible leafletvalve devices in which the leaflets have a planar central zone. Thepresence of the planar zone may be determined when the valve is notunder pressure. The planar zone is present in the form of a truncatedisosceles triangle or an isosceles trapezoid defining a truncated top.The width of the truncated top at the free edge of the leaflet is chosenso that, in the closed and fully pressurized condition, full coaptationof the leaflets is achieved.

A prosthetic valve is provided having a leaflet frame and a plurality ofleaflets. The leaflets are coupled to the leaflet frame. Each leafletincludes a free edge and a base. Each leaflet has a planar zone in acentral region, wherein the planar zone is substantially planar, whereinthe planar zone defines a shape having an area. The area is largernearer the base than the free edge. The planar zone extends to the freeedge defining a truncated top having a top width as measured along thefree edge greater than zero. Each leaflet has a coaptation zone definedby an area adjacent the free edge that is in contact with an adjacentleaflet when the leaflets are in a closed position. A coaptation heightis defined as a length of the coaptation zone measured in an axialdirection, wherein the coaptation height is greater than zero.

A method of forming a prosthetic heart valve, comprises: providing aleaflet frame having a generally tubular shape, the leaflet framedefining a plurality of leaflet windows wherein each of the leafletwindows includes two leaflet window sides, a leaflet window base, and aleaflet window top; providing a film; wrapping the film about theleaflet frame bringing more than one layer of the film into contact withadditional layers of the film defining at least one leaflet extendingfrom each of the leaflet windows; and bonding the layers of film toitself and to the leaflet frame, wherein each leaflet has substantiallya shape of an isosceles trapezoid having two leaflet sides, a leafletbase and a free edge opposite the leaflet base, wherein the two leafletsides diverge from the leaflet base, wherein the leaflet base issubstantially flat, wherein the leaflet base is coupled to the windowbase and wherein each of the two leaflet sides are coupled to one of thetwo window sides providing a generally annular support structure, eachleaflet having a planar zone in a central region, wherein the planarzone is substantially planar, wherein the planar zone defines a shapehaving an area, wherein the area is larger nearer the base than the freeedge, wherein the planar zone extends to the free edge defining atruncated top having a top width as measured along the free edge greaterthan zero, each leaflet having a coaptation zone defined by an areaadjacent the free edge that is in contact with an adjacent leaflet whenthe leaflets are in a closed position, defining a coaptation height as alength of the coaptation zone measured in an axial direction, whereinthe coaptation height is greater than zero.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the present disclosure and are incorporated in andconstitute a part of this specification, illustrate embodimentsdescribed herein, and together with the description serve to explain theprinciples discussed in this disclosure.

FIG. 1A is a side view of a prosthetic valve in accordance with anembodiment; and

FIG. 1B is a perspective view of the embodiment of the valve of FIG. 1A;

FIG. 1C is an axial view of an embodiment of the prosthetic valve ofFIG. 2A in an open configuration;

FIG. 1D is an axial view of the embodiment of the prosthetic valve ofFIG. 2A in a closed configuration;

FIG. 2 is a representation of an embodiment of a leaflet frame unrolledto a flat orientation;

FIG. 3A is a side view of an embodiment of a transcatheter deliverysystem within anatomy;

FIG. 3B is a side view of an embodiment of a surgical valve withinanatomy;

FIG. 4 is a representation of an embodiment of a leaflet frame unrolledto a flat orientation;

FIG. 5 is a perspective view of a leaflet in accordance with anotherembodiment;

FIG. 6 is a side view of the leaflet frame on an assembly mandrel, inaccordance with an embodiment;

FIG. 7A is a side view of the leaflet frame on a cutting mandrel, inaccordance with an embodiment; and

FIG. 7B is a perspective view of the leaflet frame on the assemblymandrel of FIG. 7A.

DETAILED DESCRIPTION

Persons skilled in the art will readily appreciate that various aspectsof the present disclosure can be realized by any number of methods andapparatus configured to perform the intended functions. Stateddifferently, other methods and apparatuses can be incorporated herein toperform the intended functions. It should also be noted that theaccompanying drawing figures referred to herein are not necessarilydrawn to scale, but may be exaggerated to illustrate various aspects ofthe present disclosure, and in that regard, the drawing figures shouldnot be construed as limiting.

Although the embodiments herein may be described in connection withvarious principles and beliefs, the described embodiments should not bebound by theory. For example, embodiments are described herein inconnection with prosthetic valves, more specifically cardiac prostheticvalves. However, embodiments within the scope of this disclosure can beapplied toward any valve or mechanism of similar structure and/orfunction. Furthermore, embodiments within the scope of this disclosurecan be applied in non-cardiac applications.

The term leaflet as used herein in the context of prosthetic valves is acomponent of a one-way valve wherein the leaflet is operable to movebetween an open and closed position under the influence of a pressuredifferential. In an open position, the leaflet allows blood to flowthrough the valve. In a closed position, the leaflet substantiallyblocks retrograde flow through the valve. In embodiments comprisingmultiple leaflets, each leaflet cooperates with at least one neighboringleaflet to block the retrograde flow of blood. The pressure differentialin the blood is caused, for example, by the contraction of a ventricleor atrium of the heart, such pressure differential typically resultingfrom a fluid pressure building up on one side of the leaflets whenclosed. As the pressure on an inflow side of the valve rises above thepressure on the outflow side of the valve, the leaflets opens and bloodflows therethrough. As blood flows through the valve into a neighboringchamber or blood vessel, the pressure on the inflow side equalizes withthe pressure on the outflow side. As the pressure on the outflow side ofthe valve raises above the blood pressure on the inflow side of thevalve, the leaflet returns to the closed position generally preventingretrograde flow of blood through the valve.

The term membrane as used herein refers to a sheet of materialcomprising a single composition, such as, but not limited to, expandedfluoropolymer.

The term composite material as used herein refers to a combination of amembrane, such as, but not limited to, expanded fluoropolymer, and anelastomer, such as, but not limited to, a fluoroelastomer. The elastomermay be imbibed within a porous structure of the membrane, coated on oneor both sides of the membrane, or a combination of coated on and imbibedwithin the membrane.

The term laminate as used herein refers to multiple layers of membrane,composite material, or other materials, such as elastomer, andcombinations thereof.

The term film as used herein generically refers to one or more of themembrane, composite material, or laminate.

The term biocompatible material as used herein generically refers to afilm or a biological material, such as, but not limited to, bovinepericardium.

The term leaflet window is defined as that space that a frame definesfrom which a leaflet extends. The leaflet may extend from frame elementsor adjacent to frame elements and spaced apart therefrom.

The terms native valve orifice and tissue orifice refer to an anatomicalstructure into which a prosthetic valve may be placed. Such anatomicalstructure includes, but is not limited to, a location wherein a cardiacvalve may or may not have been surgically removed. It is understood thatother anatomical structures that may receive a prosthetic valve include,but are not limited to, veins, arteries, ducts and shunts. Althoughreference is made herein to replacing a native valve with a prostheticvalve, it is understood and appreciated that a valve orifice or implantsite may also refer to a location in a synthetic or biological conduitthat may receive a valve for a particular purpose, and therefore thescope of the embodiments provided herein is not limited to valvereplacement.

As used herein, “couple” means to join, couple, connect, attach, adhere,affix, or bond, whether directly or indirectly, and whether permanentlyor temporarily.

Embodiments herein include various apparatus, systems, and methods for aprosthetic valve suitable for surgical and transcatheter placement, suchas, but not limited to, cardiac valve replacement. The valve is operableas a one-way valve wherein the valve defines a valve orifice into whichleaflets open to permit flow and close so as to occlude the valveorifice and prevent flow in response to differential fluid pressure.

The embodiments presented herein are related to controlled leafletopening. The durability of the valve leaflets is largely controlled bythe character of bending exhibited by the leaflet during theopening-closing cycle. Small radius bends, creases and particularlyintersecting creases, can produce high stress zones in the leaflet.These high stress zones can cause the formation of holes and tears underrepetitive loading.

The design specified in the current disclosure is intended to place theleaflets made from synthetic materials under a minimized stresscondition as compared to those based on copies of the native valve. Thisis partially accomplished through reduced buckling in the leafletmaterial. It has been discovered that two features of leaflet shape areof particular importance in minimizing buckling and crease formation.They are of particular importance in thin, high-modulus leaflets, sincethe bending in these materials tends to be cellophane-like. If theleaflet bending is unrestricted, not only do creases form, but creaseintersections lead to formation of large transient three dimensionalstructures that oppose bending and slow down the leaflet motion, both inopening and closing. In accordance to embodiments herein, features areprovided in the valve leaflets that allows a redundant coaptation zonein the leaflets.

Valve

FIG. 1A is a side view of a valve 100, in accordance with an embodiment.FIG. 1B is a perspective view of the valve 100 of FIG. 1A. FIGS. 1C and1D are axial views of the valve 100 of FIG. 1A in an open and closedconfiguration, respectively. The valve 100 comprises a leaflet frame 130and film 160 that defines leaflets 140. FIG. 2 is a side view of theleaflet frame 130 of the valve 100 of FIG. 1A wherein the leaflet frame130 has been longitudinally cut and laid open to better illustrate theelements of the generally tubular-shaped valve 100.

Leaflet Frame

Referring to FIGS. 1A-1D, the leaflet frame 130 is a generally tubularmember defining a generally open pattern of apertures 122, in accordancewith an embodiment. In accordance with transcatheter embodiments, theleaflet frame 130 is operable to allow it to be compressed and expandedbetween different diameters. The leaflet frame 130 comprises a framefirst end 121 a and a frame second end 121 b opposite the frame firstend 121 a. The leaflet frame 130 comprises a leaflet frame outer surface126 a and a leaflet frame inner surface 126 b opposite the leaflet frameouter surface 126 a, as shown in FIG. 1A. The leaflet frame 130 definescommissure posts 136 that couple to the leaflet free edges 142.

FIG. 4 is a side view of a leaflet frame 130 a of a valve 100 whereinthe leaflet frame 130 a has been longitudinally cut and laid open tobetter illustrate the elements of the generally tubular-shaped frame 130a, in accordance with an embodiment. The leaflet frame 130 a comprisesangular frame elements suitable for affecting compression and expansionas would be needed for intravascular placement.

The leaflet frame 130 can define any number of features, repeatable orotherwise, such as geometric shapes and/or linear or meandering seriesof sinusoids. Geometric shapes can comprise any shape that facilitatessubstantially uniform circumferential compression and expansion. Theleaflet frame 130 may comprise a cut tube, or any other element suitablefor the particular purpose. The leaflet frame 130 may be etched, cut,laser cut, or stamped into a tube or a sheet of material, with the sheetthen formed into a substantially cylindrical structure. Alternatively,an elongated material, such as a wire, bendable strip, or a seriesthereof, can be bent or braided and formed into a substantiallycylindrical structure wherein the walls of the cylinder comprise an openframework that is compressible to a smaller diameter in a generallyuniform and circumferential manner and expandable to a larger diameter.

The leaflet frame 130 can comprise any metallic or polymericbiocompatible material. For example, the leaflet frame 130 can comprisea material, such as, but not limited to nitinol, cobalt-nickel alloy,stainless steel, or polypropylene, acetyl homopolymer, acetyl copolymer,ePTFE, other alloys or polymers, or any other biocompatible materialhaving adequate physical and mechanical properties to function asdescribed herein.

It is known that stents of various designs may be elastically deformableso as to be self-expanding under spring loads. It is also known thatstents of various designs may be plastically deformable so as to bemechanically expanded such as with a balloon. It is also known thatstents of various designs may be plastically deformable as well aselastically deformable. The embodiments of the outer frame 120 presentedherein are not to be limited to a specific stent design or mode ofexpansion.

The frame 120 can comprise any metallic or polymeric biocompatiblematerial. For example, the frame 120 can comprise a material, such as,but not limited to nitinol, cobalt-nickel alloy, stainless steel, orpolypropylene, acetyl homopolymer, acetyl copolymer, ePTFE, other alloysor polymers, or any other biocompatible material having adequatephysical and mechanical properties to function as described herein.

In accordance with embodiments, the leaflet frame 130 can be configuredto provide positive engagement with an implant site to firmly anchor thevalve 100 to the site, as shown in FIG. 3A representing a transcatheterdeployment of the valve 100. In accordance with an embodiment, theleaflet frame 130 can comprise a sufficiently rigid frame having smallelastic recoil so as to maintain sufficient apposition against a tissueorifice 150 to maintain position. In accordance with another embodiment,the leaflet frame 130 can be configured to expand to a diameter that islarger than a tissue orifice 150 so that when valve 100 expands into thetissue orifice 150, it can be firmly seated therein. In accordance withanother embodiment, the leaflet frame 130 can comprise one or moreanchors (not shown) configured to engage the implant site, such as atissue orifice 150, to secure the valve 100 to the implant site.

It is appreciated that other elements or means for coupling the valve100 to an implant site are anticipated. By way of example, but notlimited thereto, other means, such as mechanical and adhesive means maybe used to couple the valve 100 to a synthetic or biological conduit.

As will be discussed later, the surgical valve 100 embodiment may or maynot have the zigzag configuration since the surgical valve 100 may be ofa fixed diameter and need not be operable to compress and re-expand.

Film

The film 160 is generally any sheet-like material that is biologicallycompatible and configured to couple to leaflets to the frame, inaccordance with embodiments. It is understood that the term “film” isused generically for one or more biocompatible materials suitable for aparticular purpose. The leaflets 140 are also comprised of the film 160.

In accordance with an embodiment, the biocompatible material is a film160 that is not of a biological source and that is sufficiently flexibleand strong for the particular purpose, such as a biocompatible polymer.In an embodiment, the film 160 comprises a biocompatible polymer that iscombined with an elastomer, referred to as a composite.

Details of various types of film 160 are discussed below. In anembodiment, the film 160 may be formed from a generally tubular materialto at least partially cover the outer frame 120 and the inner frame 130.The film 160 can comprise one or more of a membrane, composite material,or laminate. Details of various types of film 160 are discussed below.

In an embodiment, the film 160 comprises a biocompatible polymer that iscombined with an elastomer, referred to as a composite. A materialaccording to one embodiment includes a composite material comprising anexpanded fluoropolymer membrane, which comprises a plurality of spaceswithin a matrix of fibrils, and an elastomeric material. It should beappreciated that multiple types of fluoropolymer membranes and multipletypes of elastomeric materials can be combined to form a laminate whileremaining within the scope of the present disclosure. It should also beappreciated that the elastomeric material can include multipleelastomers, multiple types of non-elastomeric components, such asinorganic fillers, therapeutic agents, radiopaque markers, and the likewhile remaining within the scope of the present disclosure.

In accordance with an embodiment, the composite material includes anexpanded fluoropolymer material made from porous ePTFE membrane, forinstance as generally described in U.S. Pat. No. 7,306,729 to Bacino.

The expandable fluoropolymer, used to form the expanded fluoropolymermaterial described, may comprise PTFE homopolymer. In alternativeembodiments, blends of PTFE, expandable modified PTFE and/or expandedcopolymers of PTFE may be used. Non-limiting examples of suitablefluoropolymer materials are described in, for example, U.S. Pat. No.5,708,044, to Branca, U.S. Pat. No. 6,541,589, to Baillie, U.S. Pat. No.7,531,611, to Sabol et al., U.S. patent application Ser. No. 11/906,877,to Ford, and U.S. patent application Ser. No. 12/410,050, to Xu et al.

The expanded fluoropolymer membrane can comprise any suitablemicrostructure for achieving the desired leaflet performance. Inaccordance with an embodiment, the expanded fluoropolymer comprises amicrostructure of nodes interconnected by fibrils, such as described inU.S. Pat. No. 3,953,566 to Gore. The fibrils radially extend from thenodes in a plurality of directions, and the membrane has a generallyhomogeneous structure. Membranes having this microstructure maytypically exhibit a ratio of matrix tensile strength in two orthogonaldirections of less than 2, and possibly less than 1.5.

In another embodiment, the expanded fluoropolymer membrane has amicrostructure of substantially only fibrils, as is generally taught byU.S. Pat. No. 7,306,729, to Bacino. The expanded fluoropolymer membranehaving substantially only fibrils, can possess a high surface area, suchas greater than 20 m²/g, or greater than 25 m²/g, and in someembodiments can provide a highly balanced strength material having aproduct of matrix tensile strengths in two orthogonal directions of atleast 1.5×10⁵ MPa², and/or a ratio of matrix tensile strengths in twoorthogonal directions of less than 4, and possibly less than 1.5.

The expanded fluoropolymer membrane can be tailored to have any suitablethickness and mass to achieve the desired leaflet performance. By way ofexample, but not limited thereto, the leaflet 140 comprises an expandedfluoropolymer membrane having a thickness of about 0.1 μm. The expandedfluoropolymer membrane can possess a mass per area of about 1.15 g/m².Membranes according to an embodiment of the invention can have matrixtensile strengths of about 411 MPa in the longitudinal direction and 315MPa in the transverse direction.

Additional materials may be incorporated into the pores or within thematerial of the membranes or in between layers of membranes to enhancedesired properties of the leaflet. Composite materials described hereincan be tailored to have any suitable thickness and mass to achieve thedesired leaflet performance. Composite materials according toembodiments can include fluoropolymer membranes and have a thickness ofabout 1.9 μm and a mass per area of about 4.1 g/m².

The expanded fluoropolymer membrane combined with elastomer to form acomposite material provides the elements of the present disclosure withthe performance attributes required for use in high-cycle flexuralimplant applications, such as heart valve leaflets, in various ways. Forexample, the addition of the elastomer can improve the fatigueperformance of the leaflet by eliminating or reducing the stiffeningobserved with ePTFE-only materials. In addition, it may reduce thelikelihood that the material will undergo permanent set deformation,such as wrinkling or creasing, that could result in compromisedperformance. In one embodiment, the elastomer occupies substantially allof the pore volume or space within the porous structure of the expandedfluoropolymer membrane. In another embodiment the elastomer is presentin substantially all of the pores of the at least one fluoropolymerlayer. Having elastomer filling the pore volume or present insubstantially all of the pores reduces the space in which foreignmaterials can be undesirably incorporated into the composite. An exampleof such foreign material is calcium that may be drawn into the membranefrom contact with the blood. If calcium becomes incorporated into thecomposite material, as used in a heart valve leaflet, for example,mechanical damage can occur during cycling open and closed, thus leadingto the formation of holes in the leaflet and degradation inhemodynamics.

In an embodiment, the elastomer that is combined with the ePTFE is athermoplastic copolymer of tetrafluoroethylene (TFE) and perfluoromethylvinyl ether (PMVE), such as described in U.S. Pat. No. 7,462,675 toChang et al. As discussed above, the elastomer is combined with theexpanded fluoropolymer membrane such that the elastomer occupiessubstantially all of the void space or pores within the expandedfluoropolymer membrane to form a composite material. This filling of thepores of the expanded fluoropolymer membrane with elastomer can beperformed by a variety of methods. In one embodiment, a method offilling the pores of the expanded fluoropolymer membrane includes thesteps of dissolving the elastomer in a solvent suitable to create asolution with a viscosity and surface tension that is appropriate topartially or fully flow into the pores of the expanded fluoropolymermembrane and allow the solvent to evaporate, leaving the filler behind.

In one embodiment, the composite material comprises three layers: twoouter layers of ePTFE and an inner layer of a fluoroelastomer disposedtherebetween. Additional fluoroelastomers can be suitable and aredescribed in U.S. Publication No. 2004/0024448 to Chang et al.

In another embodiment, a method of filling the pores of the expandedfluoropolymer membrane includes the steps of delivering the filler via adispersion to partially or fully fill the pores of the expandedfluoropolymer membrane.

In another embodiment, a method of filling the pores of the expandedfluoropolymer membrane includes the steps of bringing the porousexpanded fluoropolymer membrane into contact with a sheet of theelastomer under conditions of heat and/or pressure that allow elastomerto flow into the pores of the expanded fluoropolymer membrane.

In another embodiment, a method of filling the pores of the expandedfluoropolymer membrane includes the steps of polymerizing the elastomerwithin the pores of the expanded fluoropolymer membrane by first fillingthe pores with a prepolymer of the elastomer and then at least partiallycuring the elastomer.

After reaching a minimum percent by weight of elastomer, the leafletsconstructed from fluoropolymer materials or ePTFE generally performedbetter with increasing percentages of elastomer resulting insignificantly increased cycle lives. In one embodiment, the elastomercombined with the ePTFE is a thermoplastic copolymer oftetrafluoroethylene and perfluoromethyl vinyl ether, such as describedin U.S. Pat. No. 7,462,675 to Chang et al., and other references thatwould be known to those of skill in the art. Other biocompatiblepolymers which can be suitable for use in leaflet 140 include but arenot limited to the groups of urethanes, silicones(organopolysiloxanes),copolymers of silicon-urethane, styrene/isobutylene copolymers,polyisobutylene, polyethylene-co-poly(vinyl acetate), polyestercopolymers, nylon copolymers, fluorinated hydrocarbon polymers andcopolymers or mixtures of each of the foregoing.

Leaflet

In embodiments provided herein, a coaptation feature 196 is providedthat allows a broad coaptation zone 198 defined by the leaflets adjacentto the leaflet free edges 142 when the leaflets are in a closedposition. Referring to FIG. 1A of the closed valve 100, the leaflet isdefined by a leaflet base 143, a free edge 142 and two leaflet sides 145extending from the leaflet base 145 to the free edge 142. The coaptationzone 198 is that area of a leaflet 140 that is in contact with anadjacent leaflet 140. A coaptation height Hc is defined as that lengthmeasured in the axial direction along axis X of the leaflet that is incontact with an adjacent leaflet 140. Generally, the coaptation heightHc is measured from the leaflet free edge 142 to a location away fromthe leaflet free edge 142 where the adjacent leaflets 140 are no longerin contact. It is understood that the coaptation height Hc may varyacross the leaflet free edge 142.

A broad coaptation zone 198 is desirable for, among other things toensure full coaptation of the leaflets 140 in the case of atranscatheter valve 100 being placed in an out-of-round native orificelocation that may result in an out-of-round valve frame 130 onceexpanded. In the out-of-round state, the leaflet free edges 142 may notproperly come into contact with adjacent leaflet free edges 142. Ifcomplete coaptation is not achieved, regurgitant flow will resultthrough the leaflet free edges 142 at the uncoapted locations.

A broad coaptation zone is also desirable for, among other things toprevent prolapse of the leaflets 140.

Though other leaflet geometry factors also contribute, prolapse canoccur when no coaptation height Hc is present, wherein the contactbetween adjacent leaflets when the valve 100 is closed. In this casevery little load sharing between the leaflets 140 occurs during fullback pressure and the leaflets 140 can prolapse and not seal.

FIG. 5 is a perspective view of a leaflet 140 comprising a verticalportion 197 that has been molded adjacent to the leaflet free edge 142defined by a fold line 199 and the leaflet free edge 142. In contrast toembodiments presented herein, the central region 182 does not comprise atruncated top; that is, the triangular planar portion defines an apex195 with zero width, with the vertical portion 197 extending therefrom.In thin, high-modulus materials however, this configuration results in apermanent fold that causes a resistance to bending with resultant poorhemodynamics.

Referring to FIGS. 1A, 1B, and 2, each leaflet window 137 is providedwith a biocompatible material, such as a film 160, which is coupled to aportion of the leaflet window sides 133 with the film 160 defining aleaflet 140. Each leaflet 140 defines a leaflet free edge 142 and aleaflet base 143, in accordance with an embodiment. As will be describedbelow, it is anticipated that a plurality of embodiments of leaflet baseconfigurations may be provided. In accordance with an embodiment, thefilm 160 is coupled to a portion of the leaflet window sides 133 and tothe leaflet window base 134 where the leaflet 140 is defined by theportion of the leaflet window sides 133 and to the leaflet window base134. In accordance with another embodiment, the film 160 is coupled to aportion of the leaflet window sides

When the leaflets 140 are in a fully open position, the valve 100presents a substantially circular valve orifice 102 as shown in FIG. 1C.Fluid flow is permitted through the valve orifice 102 when the leaflets140 are in an open position.

As the leaflets 140 cycle between the open and closed positions, theleaflets 140 generally flex about the leaflet base 143 and the portionof the leaflet window sides 133 to which the leaflet are coupled. Whenthe valve 100 is closed, generally about half of each leaflet free edge142 abuts an adjacent half of a leaflet free edge 142 of an adjacentleaflet 140, as shown in FIG. 1D. The three leaflets 140 of theembodiment of FIG. 1D meet at a triple point 148. The valve orifice 102is occluded when the leaflets 140 are in the closed position stoppingfluid flow.

Referring to FIG. 1D, in accordance with an embodiment, each leaflet 140includes a central region 182 and two side regions 184 on opposite sidesof the central region 182. The central region 182 is defined by a shapesubstantially that of a triangle defined by two central region sides183, the leaflet base 143 and the free edge 142. The two central regionsides 183 converge from the leaflet base 143 to the free edge 142.

In accordance with an embodiment, the central region 182 issubstantially planar, defining a planar zone 192, when the valve 100 isin the closed position and not under fluid pressure. The planar zone 192has a shape substantially of an isosceles triangle with apices extendingto the leaflet frame 130. Referring to FIG. 1D, an apex line La isindicated connecting the apices 147 of the leaflets 140. The apex lineLa divides the leaflet 140 into a first region 149 a adjacent theleaflet frame 130, and a second region 149 b adjacent the leaflet freeedge. The first region 149 a contains a larger proportion of planar zone192 than the second region 149 b. In other embodiments, the majority ofthe planar zone 192 of each leaflet 140 is located inferior and exteriorto apex line La joining the apices of two adjacent commissure posts 136.The ratio of area of the planar zone 192 distributed in the first region149 a and second region 149 b has been found to produce better leafletopening dynamics than if there were more area of the planar zone 192distributed in the second region 149 b than the first region 149 a.

As shown in FIG. 1A, in accordance with an embodiment, the planar zone192 has a shape substantially of an isosceles triangle with apicesextending to the leaflet frame 130. The planar zone 192 extends to thefree edge 142 of the leaflet 140 defining a truncated top 193 of theisosceles triangle having a width Hp. As shown, therefore, the planarzone 192 has a truncated top 193 with a width Hp greater than zero.

The leaflet 140 can be configured to actuate at a pressure differentialin the blood caused, for example, by the contraction of a ventricle oratrium of the heart, such pressure differential typically resulting froma fluid pressure building up on one side of the valve 100 when closed.As the pressure on an inflow side of the valve 100 rises above thepressure on the outflow side of the valve 100, the leaflet 140 opens andblood flows therethrough. As blood flows through the valve 100 into aneighboring chamber or blood vessel, the pressure equalizes. As thepressure on the outflow side of the valve 100 rises above the bloodpressure on the inflow side of the valve 100, the leaflet 140 returns tothe closed position generally preventing the retrograde flow of bloodthrough the inflow side of the valve 100.

It is understood that the leaflet frame 130 may comprise any number ofleaflet windows 137, and thus leaflets 140, suitable for a particularpurpose, in accordance with embodiments. Leaflet frames 130 comprisingone, two, three or more leaflet windows 137 and corresponding leaflets140 are anticipated.

In accordance with an embodiment of a valve 100 suitable fortranscatheter placement, the valve 100 may be compressed into acollapsed configuration having a smaller diameter and expanded into anexpanded configuration so that the valve 100 can be delivered viacatheter in the collapsed configuration and expanded upon deploymentwithin the tissue orifice 150 as shown in FIG. 3A. The leaflet frame 130can be operable to recover circumferential uniformity when transitioningfrom the collapsed configuration to the expanded configuration.

The valve 100 may be mounted onto a delivery catheter, suitable for aparticular purpose. The diameter of the valve 100 in the collapsedconfiguration is determined in part by the thickness of the frame andthe leaflet thickness.

Other Considerations

In accordance with an embodiment, the valve 100 can be configured toprevent interference with a heart conduction system by not covering abundle branch in the left ventricle when implanted, such as might beencountered with an aortic valve replacement procedure. For example, thevalve 100 can comprise a length of less than about 25 mm or less thanabout 18 mm. The valve 100 can also comprise an aspect ratio of lessthan one, wherein the ratio describes the relationship between thelength of the valve 100 to the expanded, functional diameter. However,the valve 100 can be constructed at any length and, more generally, anydesirable dimension.

In a transcatheter embodiment, in a collapsed state, the valve 100 canhave a collapsed profile that is less than about 35% of the expandedprofile. For example, the valve 100 comprising a 26 mm expanded diametercan have a collapsed diameter of less than about 8 mm, or less thanabout 6 mm. The percent difference in diameter is dependent ondimensions and materials of the valve 100 and its various applications,and therefore, the actual percent difference is not limited by thisdisclosure.

The valve 100 can further comprise a bio-active agent. Bio-active agentscan be coated onto a portion or the entirety of the film 160 forcontrolled release of the agents once the valve 100 is implanted. Thebio-active agents can include, but are not limited to, vasodilator,anti-coagulants, anti-platelet, anti-thrombogenic agents such as, butnot limited to, heparin. Other bio-active agents can also include, butare not limited to agents such as, for example,anti-proliferative/antimitotic agents including natural products such asvinca alkaloids (i.e. vinblastine, vincristine, and vinorelbine),paclitaxel, epidipodophyllotoxins (i.e. etoposide, teniposide),antibiotics (dactinomycin (actinomycin D) daunorubicin, doxorubicin andidarubicin), anthracyclines, mitoxantrone, bleomycins, plicamycin(mithramycin) and mitomycin, enzymes (L-asparaginase which systemicallymetabolizes L-asparagine and deprives cells which do not have thecapacity to synthesize their own asparagine); antiplatelet agents suchas G(GP) IIb/IIIa inhibitors and vitronectin receptor antagonists;anti-proliferative/antimitotic alkylating agents such as nitrogenmustards (mechlorethamine, cyclophosphamide and analogs, melphalan,chlorambucil), ethylenimines and methylmelamines (hexamethylmelamine andthiotepa), alkyl sulfonates-busulfan, nitrosoureas (carmustine (BCNU)and analogs, streptozocin), trazenes-dacarbazinine (DTIC);anti-proliferative/antimitotic antimetabolites such as folic acidanalogs (methotrexate), pyrimidine analogs (fluorouracil, floxuridine,and cytarabine), purine analogs and related inhibitors (mercaptopurine,thioguanine, pentostatin and 2-chlorodeoxyadenosine{cladribine});platinum coordination complexes (cisplatin, carboplatin), procarbazine,hydroxyurea, mitotane, aminoglutethimide; hormones (i.e. estrogen);anti-coagulants (heparin, synthetic heparin salts and other inhibitorsof thrombin); fibrinolytic agents (such as tissue plasminogen activator,streptokinase and urokinase), aspirin, dipyridamole, ticlopidine,clopidogrel, abciximab; antimigratory; antisecretory (breveldin);anti-inflammatory: such as adrenocortical steroids (cortisol, cortisone,fludrocortisone, prednisone, prednisolone, 6α-methylprednisolone,triamcinolone, betamethasone, and dexamethasone), non-steroidal agents(salicylic acid derivatives i.e. aspirin; para-aminophenol derivativesi.e. acetominophen; indole and indene acetic acids (indomethacin,sulindac, and etodalac), heteroaryl acetic acids (tolmetin, diclofenac,and ketorolac), arylpropionic acids (ibuprofen and derivatives),anthranilic acids (mefenamic acid, and meclofenamic acid), enolic acids(piroxicam, tenoxicam, phenylbutazone, and oxyphenthatrazone),nabumetone, gold compounds (auranofin, aurothioglucose, gold sodiumthiomalate); immunosuppressives: (cyclosporine, tacrolimus (FK-506),sirolimus (rapamycin), azathioprine, mycophenolate mofetil); angiogenicagents: vascular endothelial growth factor (VEGF), fibroblast growthfactor (FGF); angiotensin receptor blockers; nitric oxide donors;anti-sense oligionucleotides and combinations thereof; cell cycleinhibitors, mTOR inhibitors, and growth factor receptor signaltransduction kinase inhibitors; retenoids; cyclin/CDK inhibitors; HMGco-enzyme reductase inhibitors (statins); and protease inhibitors.

Transcatheter Delivery System

In an embodiment, with reference to FIG. 3A, a valve delivery system 500comprises a valve 100 having a collapsed configuration and an expandedconfiguration as previously described and an elongated flexible catheter480, such as a balloon catheter, configured to deploy the valve 100 viacatheter. The catheter 480 can comprise a balloon to expand the valve100 and/or if required, to touch up the valve 100 to ensure properseating. The valve 100 can be mounted to the distal section of thecatheter 480 for delivery through the vasculature. In order to hold thevalve in a collapsed configuration on the catheter 480, the valvedelivery system may further comprise a removable sheath (not shown) toclosely fit over the transcatheter valve 100.

A method of delivery can comprise the steps of radially compressing avalve into its collapsed configuration onto the distal end of anelongate flexible catheter having proximal and distal ends; deliveringthe valve to a tissue orifice, such as a native aortic valve orifice,via a transfemoral or transapical route, and expanding the valve intothe tissue orifice. The valve can be expanded by inflating a balloon.

A method of delivery can comprise the steps of radially compressing avalve into its collapsed configuration, onto the distal section of anelongated flexible catheter having proximal and distal ends. Arestraint, which can be connected to a tether that passes through theorifice of valve and the lumen of the catheter, is fitted around theposts of the valve. The valve is then delivered to a native valveorifice, such as a native aortic valve orifice, via a route of deliveryand expanded into the native orifice. The route of delivery can comprisea transfemoral or transapical route. The valve can be expanded byinflating a balloon.

Surgical Embodiments

It is appreciated that the embodiments of the valve 100 may besurgically implanted rather than using transcatheter techniques.Embodiments of a surgically implanted valve 100 may be substantially thesame as those described above, with the addition of a sewing cuff 170adjacent to the leaflet frame outer surface 126 a, shown in FIG. 3B, inaccordance with an embodiment. The sewing cuff, which is well known inthe art, is operable to provide structure that receives suture forcoupling the valve 100 to an implant site, such as the tissue orifice.The sewing cuff may comprise any suitable material, such as, but notlimited to, double velour polyester. The sewing cuff may be locatedcircumferentially around the leaflet frame 130 or perivalvular dependingfrom the leaflet frame 130.

Method of Making

Embodiments described herein also pertain to a method of making thevalve 100 embodiments as described herein. In order to make the variousembodiments, a cylindrical mandrel 710 can be used. With reference toFIG. 6, the mandrel 710 comprises a structural form operable to receivethe leaflet frame 130 thereon.

Embodiments described herein also pertain to a method of making thevalve 100 embodiments as described herein. In order to make the variousembodiments, a cylindrical mandrel 710 can be used. With reference toFIG. 6, the mandrel 710 comprises a structural form operable to receivethe leaflet frame 130 thereon. An embodiment of a method of making avalve 100 comprises the steps of wrapping a first layer of film 160,e.g., a composite as described herein, into a tubular form about themandrel 710; placing the leaflet frame 130 over the first layer of film160, as shown in FIG. 6; forming a second layer of film 160 over theleaflet frame 130; thermally setting the assembly; receiving theassembly over a cutting mandrel 712 as shown in FIGS. 8A and 8B; cuttingthe film 160 across the leaflet window top within the leaflet window 137

EXAMPLE

In exemplary embodiments, a heart valve having polymeric leaflets formedfrom a composite material having an expanded fluoropolymer membrane andan elastomeric material and joined to a semi-rigid, non-collapsiblemetallic frame, and further a having strain relief was constructedaccording to the following process:

A leaflet frame 130 was laser machined from a length of MP35N cobaltchromium tube hard tempered with an outside diameter of 26.0 mm and awall thickness of 0.6 mm in the shape. The leaflet frame waselectro-polished resulting in 0.0127 mm material removal from eachsurface and leaving the edges rounded. The leaflet frame was exposed toa surface roughening step to improve adherence of leaflets to theleaflet frame. The leaflet frame was cleaned by submersion in anultrasonic bath of acetone for approximately five minutes. The entiremetal frame surface was then subjected to a plasma treatment usingequipment (e.g. PVA TePLa America, Inc Plasma Pen, Corona, Calif.) andmethods commonly known to those having ordinary skill in the art. Thistreatment also served to improve the wetting of the fluorinated ethylenepropylene (FEP) adhesive.

FEP powder (Daikin America, Orangeburg N.Y.) was then applied to theleaflet frame. More specifically, the FEP powder was stirred to form anairborne “cloud” in an enclosed blending apparatus, such as a standardkitchen type blender, while the leaflet frame is suspended in the cloud.The leaflet frame was exposed to the FEP powder cloud until a layer ofpowder was adhered to the entire surface of the leaflet frame. Theleaflet frame was then subjected to a thermal treatment by placing it ina forced air oven set to 320° C. for approximately three minutes. Thiscaused the powder to melt and adhere as a thin coating over the entireleaflet frame. The leaflet frame was removed from the oven and left tocool to approximately room temperature.

The strain relief was attached to the leaflet frame in the followingmanner. A thin (122 μm) walled sintered 15 mm diameter ePTFE tube wasdisposed on a 24.5 mm vented metal mandrel by stretching radially over atapered mandrel. Two layers of a substantially nonporous ePTFE membranewith a continuous FEP coating was circumferentially wrapped on themandrel with the FEP side towards the mandrel. The wrapped mandrel wasplaced in a convection oven set to 320° C. and heated for 20 min. TheePTFE and substantially nonporous ePTFE membrane combined to serve as aninner release liner and was perforated using a scalpel blade tocommunicate pressure between the vent holes in the mandrel. This entirerelease liner is removed in a later step.

A 5 cm length of the thick (990μ) walled partially sintered 22 mm innerdiameter ePTFE tube (density=0.3 g/cm³) was disposed onto the 24.5 mmvented metal mandrel with release liner. The ePTFE tube inner diameterwas enlarged by stretching it on a tapered mandrel to accommodate thelarger mandrel diameter.

A thin (4 μm) film of type 1 FEP (ASTM D3368) was constructed using meltextrusion and stretching. One layer of the FEP was wrapped over the 5 cmlength of the ePTFE tube.

The FEP powder coated leaflet frame was disposed onto the vented metalmandrel generally in the middle of the 5 cm span of ePTFE tube and FEPfilm.

One layer of the FEP was wrapped over the leaflet frame and 5 cm lengthof the ePTFE tube.

A second 5 cm length of the 990 μm thick/22 mm inner diameter ePTFE tubewas disposed onto the assembly layered onto 24.5 mm vented metal mandrelby stretching its radius over a tapered mandrel to accommodate thelarger construct diameter.

A substantially nonporous ePTFE membrane was configured into a cylinderat a diameter larger than the construct and placed over the assembly,referred to as sacrificial tube. Sintered ePTFE fiber (e.g. Gore Rastex®Sewing Thread, Part #S024T2, Newark Del.) was used to seal both ends ofthe sacrificial tube against the mandrel.

The assembly, including the mandrel, was heated in a convection oven(temperature set point of 390° C.) capable of applying pneumaticpressure of 100 psi external to the sacrificial tube described abovewhile maintaining a vacuum internal to the mandrel. The assembly wascooked for 40 min such that the mandrel temperature reachedapproximately 360° C. (as measured by a thermocouple direct contact withthe inner diameter of the mandrel). The assembly was removed from theoven and allowed to cool to approximately room temperature while stillunder 100 psi pressure and vacuum.

The sacrificial tube was then removed. Approximately 30 psi of pressurewas applied to the internal diameter of the mandrel to assist in removalof the assembly. The inner release liner was peeled away from theinternal diameter of the assembly by inverting the liner and axiallypulling it apart.

A leaflet material was then prepared. A membrane of ePTFE wasmanufactured according to the general teachings described in U.S. Pat.No. 7,306,729. The ePTFE membrane had a mass per area of 0.452 g/m², athickness of about 508 nm, a matrix tensile strength of 705 MPa in thelongitudinal direction and 385 MPa in the transverse direction. Thismembrane was imbibed with a fluoroelastomer. The copolymer consistsessentially of between about 65 and 70 weight percent perfluoromethylvinyl ether and complementally about 35 and 30 weight percenttetrafluoroethylene.

The fluoroelastomer was dissolved in Novec HFE7500 (3M, St Paul, Minn.)in a 2.5% concentration. The solution was coated using a mayer bar ontothe ePTFE membrane (while being supported by a polypropylene releasefilm) and dried in a convection oven set to 145° C. for 30 seconds.After 2 coating steps, the final ePTFE/fluoroelastomer or composite hada mass per area of 1.75 g/m², 29.3% fluoropolymer by weight, a domeburst strength of about 8.6 KPa, and thickness of 0.81 μm.

The leaflet material was then attached in a cylindrical or tubular shapeto the valve frame encapsulated with polymeric material defining astrain relief in the following manner. A release liner was disposed on a24.5 mm vented mandrel and perforated using a scalpel blade tocommunicate pressure between the vent holes in the mandrel.

The leaflet frame with polymeric strain relief was disposed onto therelease liner covering the vented metal mandrel generally in the middleof the 100 cm span of the mandrel.

Sixty-two layers of leaflet material were wrapped over the leaflet frameand 100 cm length of the mandrel. Excess leaflet material was trimmedaway with a scalpel from the mandrel adjacent to the vent holes.

A sacrificial tube was placed over the assembly and Rastex® fiber wasused to seal both ends of the sacrificial tube against the mandrel.

The assembly, including the mandrel, was heated in a convection oven(temperature set point of 390° C.) capable of applying pneumaticpressure of 100 psi external to the sacrificial tube described abovewhile maintaining a vacuum internal to the mandrel. The assembly wascooked for 23 minutes such that the mandrel temperature reachedapproximately 285° C. (as measured by a thermocouple direct contact withthe inner diameter of the mandrel). The assembly was removed from theoven and allowed to cool to approximately room temperature while stillunder 100 psi pressure and vacuum.

The Rastex® fiber and sacrificial tube were then removed. Approximately30 psi of pressure was applied to the inside of the mandrel to assist inremoval of the assembly. The inner release liner was peeled away fromthe internal diameter of the assembly by inverting the liner and axiallypulling it apart.

The cylindrical shape of the leaflet frame and leaflet assembly was thenmolded into the final closed leaflet geometry in the following manner.The assembly was placed onto a 24.5 mm vented mandrel with a cavitydefining the closed geometry of the leaflets.

Rastex® fiber was used to seal both ends of the leaflet tube against thecircumferential grooves in the mandrel.

The assembly, including the mandrel, was heated in a convection oven(temperature set point of 390° C.) capable of applying pneumaticpressure of 100 psi external to the sacrificial tube described abovewhile maintaining a vacuum internal to the mandrel. The assembly wascooked for 23 minutes such that the mandrel temperature reachedapproximately 285° C. (as measured by a thermocouple direct contact withthe inner diameter of the mandrel). The assembly was removed from theoven and allowed to cool to approximately room temperature while stillunder 100 psi pressure and vacuum. The Rastex® fiber was then removedand approximately 10 psi of pressure was applied to the internaldiameter of the mandrel to assist in removal of the assembly.

Excess leaflet material was trimmed generally along the free edge linedepicted in a cavity mold 714 of the cutting mandrel 712 shown in FIGS.7A and 7B. The final leaflet was comprised of 28.22% fluoropolymer byweight with a thickness of 50.3 μm. Each leaflet had 62 layers of thecomposite and a ratio of thickness/number of layers of 0.81 μm.

The resulting valve included leaflets formed from a composite materialwith more than one fluoropolymer layer having a plurality of pores andan elastomer present in substantially all of the pores of the more thanone fluoropolymer layer. Each leaflet was movable between a closedposition, shown illustratively in FIG. 1D, in which fluid wassubstantially prevented from flowing through the valve, and an openposition, shown illustratively in FIG. 1C, in which fluid was allowed toflow through the valve.

The performance of the valve leaflets was characterized on a real-timepulse duplicator that measured typical anatomical pressures and flowsacross the valve. The flow performance was characterized by thefollowing process:

The valve assembly was potted into a silicone annular ring (supportstructure) to allow the valve assembly to be subsequently evaluated in areal-time pulse duplicator. The potting process was performed accordingto the recommendations of the pulse duplicator manufacturer (ViVitroLaboratories Inc., Victoria BC, Canada)

The potted valve assembly was then placed into a real-time left heartflow pulse duplicator system. The flow pulse duplicator system includedthe following components supplied by VSI Vivitro Systems Inc., VictoriaBC, Canada: a Super Pump, Servo Power Amplifier Part Number SPA 3891; aSuper Pump Head, Part Number SPH 5891 B, 38.320 cm² cylinder area; avalve station/fixture; a Wave Form Generator, TriPack Part Number TP2001; a Sensor Interface, Part Number VB 2004; a Sensor AmplifierComponent, Part Number AM 9991; and a Square Wave Electro Magnetic FlowMeter, Carolina Medical Electronics Inc., East Bend, N.C., USA.

In general, the flow pulse duplicator system uses a fixed displacement,piston pump to produce a desired fluid flow through the valve undertest.

The heart flow pulse duplicator system was adjusted to produce thedesired flow (5 L/minutes), mean pressure (15 mmHg), and simulated pulserate (70 bpm). The valve under test was then cycled for about 5 to 20minutes.

Pressure and flow data were measured and collected during the testperiod, including right ventricular pressures, pulmonary pressures, flowrates, and pump piston position. Parameters used to characterize thevalve are effective orifice area and regurgitant fraction. The effectiveorifice area (EOA), which can be calculated as follows:EOA(cm²)=Q_(rms)/(51.6*(ΔP)^(1/2)) where Q_(rms) is the root mean squaresystolic/diastolic flow rate (cm³/s) and ΔP is the meansystolic/diastolic pressure drop (mmHg).

Another measure of the hydrodynamic performance of a valve is theregurgitant fraction, which is the amount of fluid or blood regurgitatedthrough the valve divided by the stroke volume.

The hydrodynamic performance was measured prior to accelerated weartesting. The performance values were; EOA=2.4 cm² and regurgitantfraction=11.94%.

As used in this application, the surface area per unit mass, expressedin units of m²/g, was measured using the Brunauer-Emmett-Teller (BET)method on a Coulter SA3100Gas Adsorption Analyzer, Beckman Coulter Inc.Fullerton Calif., USA. To perform the measurement, a sample was cut fromthe center of the expanded fluoropolymer membrane and placed into asmall sample tube. The mass of the sample was approximately 0.1 to 0.2g. The tube was placed into the Coulter SA-Prep Surface Area Outgasser(Model SA-Prep, P/n 5102014) from Beckman Coulter, Fullerton Calif., USAand purged at about 110° C. for about two hours with helium. The sampletube was then removed from the SA-Prep Outgasser and weighed. The sampletube was then placed into the SA3100 Gas adsorption Analyzer and the BETsurface area analysis was run in accordance with the instrumentinstructions using helium to calculate the free space and nitrogen asthe adsorbate gas.

Membrane thickness was measured by placing the membrane between the twoplates of a Käfer FZ1000/30 thickness snap gauge Käfer MessuhrenfabrikGmbH, Villingen-Schwenningen, Germany. The average of the threemeasurements was reported.

The presence of elastomer within the pores can be determined by severalmethods known to those having ordinary skill in the art, such as surfaceand/or cross section visual, or other analyses. These analyses can beperformed prior to and after the removal of elastomer from the leaflet.

Membrane samples were die cut to form rectangular sections about 2.54 cmby about 15.24 cm to measure the weight (using a Mettler-Toledoanalytical balance model AG204) and thickness (using a Käfer Fz1000/30snap gauge). Using these data, density was calculated with the followingformula: ρ=m/w*l*t, in which: ρ=density (g/cm³): m=mass (g), w=width(cm), l=length (cm), and t=thickness (cm. The average of threemeasurements was reported.

Tensile break load was measured using an INSTRON 122 tensile testmachine equipped with flat-faced grips and a 0.445 kN load cell. Thegauge length was about 5.08 cm and the cross-head speed was about 50.8cm/min. The sample dimensions were about 2.54 cm by about 15.24 cm. Forlongitudinal measurements, the longer dimension of the sample wasoriented in the highest strength direction. For the orthogonal MTSmeasurements, the larger dimension of the sample was orientedperpendicular to the highest strength direction. Each sample was weighedusing a Mettler Toledo Scale Model AG204, then the thickness measuredusing the Käfer FZ1000/30 snap gauge. The samples were then testedindividually on the tensile tester. Three different sections of eachsample were measured. The average of the three maximum loads (i.e., peakforce) measurements was reported. The longitudinal and transverse matrixtensile strengths (MTS) were calculated using the following equation:MTS=(maximum load/cross-section area)*(bulk density of PTFE)/(density ofthe porous membrane), wherein the bulk density of the PTFE was taken tobe about 2.2 g/cm³. Flexural stiffness was measured by following thegeneral procedures set forth in ASTM D790. Unless large test specimensare available, the test specimen must be scaled down. The testconditions were as follows. The leaflet specimens were measured on athree-point bending test apparatus employing sharp posts placedhorizontally about 5.08 mm from one another. An about 1.34 mm diametersteel bar weighing about 80 mg was used to cause deflection in the y(downward) direction, and the specimens were not restrained in the xdirection. The steel bar was slowly placed on the center point of themembrane specimen. After waiting about 5 minutes, the y deflection wasmeasured. Deflection of elastic beams supported as above can berepresented by: d=F*L³/48*EI, where F (in Newtons) is the load appliedat the center of the beam length, L (meters), so L=½ distance betweensuspending posts, and EI is the bending stiffness (Nm). From thisrelationship the value of EI can be calculated. For a rectangularcross-section: I=t³*w/12, where I=cross-sectional moment of inertia,t=specimen thickness (meters), w=specimen width (meters). With thisrelationship, the average modulus of elasticity over the measured rangeof bending deflection can be calculated.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present embodimentswithout departing from the spirit or scope of the embodiments. Thus, itis intended that the present embodiments cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A prosthetic valve comprising: a leaflet frame;and a plurality of leaflets coupled to the leaflet frame, each leafletincluding a free edge and a leaflet base, each leaflet having a planarzone in a central region, wherein the planar zone is substantiallyplanar, wherein the planar zone defines a shape having an area, whereinthe area is larger nearer the leaflet base than the free edge, whereinthe planar zone extends to the free edge defining a truncated top havinga top width as measured along the free edge greater than zero, eachleaflet having a coaptation zone defined by an area adjacent the freeedge that is in contact with an adjacent leaflet when the leaflets arein a closed position defining a coaptation height as a length of thecoaptation zone measured in an axial direction, wherein the coaptationheight is greater than zero.
 2. The prosthetic valve of claim 1, theleaflet frame having a generally tubular shape, the leaflet framedefining a plurality of leaflet windows wherein each of the leafletwindows includes two leaflet window sides, and a leaflet window base,two adjacent leaflet window sides terminating at a commissure post, amajority of the planar zone of each leaflet being located inferior andexterior to a line joining apices of two adjacent commissure posts. 3.The prosthetic valve of claim 1, wherein the central region issubstantially planar.
 4. The prosthetic valve of claim 1, wherein theplanar zone has a shape substantially of a triangle.
 5. The prostheticvalve of claim 1, wherein the planar zone has a shape substantially ofan isosceles triangle.
 6. The prosthetic valve of claim 1, wherein theplanar zone has a shape substantially of an isosceles trapezoid.
 7. Theprosthetic valve of claim 1, wherein each leaflet has substantially theshape of an isosceles trapezoid having two leaflet sides, a leaflet baseand a free edge opposite the leaflet base, wherein the planar zoneextends to the free edge of the leaflet.
 8. The prosthetic valve ofclaim 1, wherein the leaflet frame has a generally tubular shape, theleaflet frame defining a plurality of leaflet windows wherein each ofthe leaflet windows includes two leaflet window sides, and a leafletwindow base, wherein the leaflet base is coupled to the window base andwherein each of the two leaflet sides are coupled to one of the twowindow sides, wherein the planar zone extends to the leaflet base. 9.The prosthetic valve of claim 1, the leaflet frame having a generallytubular shape, the leaflet frame defining a plurality of leaflet windowswherein each of the leaflet windows includes two leaflet window sides, aleaflet window base, and a leaflet window top; and a film coupled to theleaflet frame and defining at least one leaflet extending from each ofthe leaflet windows, wherein each leaflet has substantially the shape ofan isosceles trapezoid having two leaflet window sides, a leaflet baseand a free edge opposite the leaflet base, wherein the two leaflet sidesdiverge from the leaflet base, wherein the leaflet base is substantiallyflat, wherein the leaflet base is coupled to the window base and whereineach of the two leaflet sides are coupled to one of the two windowsides.
 10. The prosthetic valve of claim 1, wherein each leaflet isdefined by two leaflet sides, the leaflet base and the free edge,wherein each leaflet includes a central region and two side regions onopposite sides of the central region, wherein the central region isdefined by a shape substantially that of an isosceles triangle definedby two central region sides, the leaflet base and the free edge, whereinthe two central region sides converge from the leaflet base, and whereineach of the side regions have a shape substantially that of a triangleand each are defined by one of the central region sides, one of theleaflet sides, and the free edge, wherein the central region is planar.11. The prosthetic valve of claim 10, wherein each of the two sideregions and the central region are substantially planar when theprosthetic valve is in a closed position under unpressurized conditions.12. The prosthetic valve of claim 2, wherein the leaflet frame comprisesa leaflet frame first end and a leaflet frame second end opposite theleaflet frame first end, the leaflet window having a shape determined,at least in part, by wrapping a two dimensional isosceles trapezoid ontoa tubular shape of the leaflet frame, the isosceles trapezoid having abase and two sides that diverge from the base, and wherein a side fromadjacent isosceles trapezoids meet at the leaflet frame second end. 13.The prosthetic valve of claim 12, further comprising a vertical elementextending from where the adjacent isosceles trapezoids meet, thevertical element having a length extending to the leaflet frame secondend.
 14. The prosthetic valve of claim 9, wherein the film is coupled toan outer surface of the leaflet frame, wherein the film defines theleaflet extending from each of the leaflet windows.
 15. The prostheticvalve of claim 9, wherein the film is coupled to an inner surface of theleaflet frame, wherein the film defines the leaflet extending from eachof the leaflet windows.
 16. The prosthetic valve of claim 9, wherein thefilm is coupled to an inner surface and an outer surface of the leafletframe, wherein the film defines the leaflet extending from each of theleaflet windows.
 17. The prosthetic valve of claim 1, wherein theleaflet frame defines three interconnected leaflet windows having asubstantially triangular shape.
 18. The prosthetic valve of claim 1,wherein a leaflet window side of one leaflet window is interconnectedwith a leaflet window side of an adjacent leaflet window.
 19. Theprosthetic valve of claim 1, wherein the leaflet frame comprises aplurality of spaced apart leaflet windows each defining substantially anisosceles triangle interconnected by a base element therebetween,wherein each leaflet window side is defined by a side of one triangleand a side of an adjacent triangle, and wherein each leaflet window baseis defined by the base element.
 20. The prosthetic valve of claim 1,wherein the leaflet frame comprises a plurality of spaced apartinterconnected leaflet windows, each leaflet window definingsubstantially isosceles trapezoids, wherein each leaflet window side isdefined by the window sides of the isosceles trapezoid, and wherein eachleaflet window base is defined by a base element.
 21. The prostheticvalve of claim 1, wherein the prosthetic valve comprises a collapsedconfiguration and an expanded configuration for transcatheter delivery.22. The prosthetic valve of claim 1, wherein the leaflet comprises apolymeric material.
 23. The prosthetic valve of claim 22, wherein theleaflet comprises a laminate.
 24. The prosthetic valve of claim 23,wherein the laminate has more than one layer of a fluoropolymermembrane.
 25. The prosthetic valve of claim 1, wherein the leafletcomprises a film having at least one fluoropolymer membrane layer havinga plurality of pores and an elastomer present in substantially all ofthe pores of at least one layer of fluoropolymer membrane.
 26. Theprosthetic valve of claim 25, wherein the film comprises less than about80% fluoropolymer membrane by weight.
 27. The prosthetic valve of claim25, wherein the elastomer comprises (per)fluoroalkylvinylethers (PAVE).28. The prosthetic valve of claim 25, wherein the elastomer comprises acopolymer of tetrafluoroethylene and perfluoromethyl vinyl ether. 29.The prosthetic valve of claim 25, wherein the fluoropolymer membranecomprises ePTFE.
 30. A method of forming a prosthetic heart valve,comprising: providing a leaflet frame having a generally tubular shape,the leaflet frame defining a plurality of leaflet windows wherein eachof the leaflet windows includes two leaflet window sides, a leafletwindow base, and a leaflet window top; providing a film; wrapping thefilm about the leaflet frame bringing more than one layer of the filminto contact with additional layers of the film defining at least oneleaflet extending from each of the leaflet windows; and bonding thelayers of film to itself and to the leaflet frame, wherein each leaflethas substantially a shape of an isosceles trapezoid having two leafletsides, a leaflet base and a free edge opposite the leaflet base, whereinthe two leaflet sides diverge from the leaflet base, wherein the leafletbase is substantially flat, wherein the leaflet base is coupled to thewindow base and wherein each of the two leaflet sides are coupled to oneof the two window sides providing a generally annular support structure,each leaflet having a planar zone in a central region, wherein theplanar zone is substantially planar, wherein the planar zone defines ashape having an area, wherein the area is larger nearer the base thanthe free edge, wherein the planar zone extends to the free edge defininga truncated top having a top width as measured along the free edgegreater than zero, each leaflet having a coaptation zone defined by anarea adjacent the free edge that is in contact with an adjacent leafletwhen the leaflets are in a closed position, defining a coaptation heightas a lenght of the coaptation zone measured in an axial direction,wherein the coaptation height is greater than zero.
 31. The method offorming a prosthetic heart valve of claim 30, wherein providing aleaflet frame comprises providing a leaflet frame having a plurality ofspaced apart leaflet windows each defining substantially an isoscelestriangle interconnected by a base element therebetween, wherein eachleaflet window side is defined by a side of one triangle and a side ofan adjacent triangle, and wherein each leaflet window base is defined bythe base element.
 32. The method of forming a prosthetic heart valve ofclaim 30, wherein providing a leaflet frame comprises providing aleaflet frame having a plurality of spaced apart interconnected leafletwindows each defining substantially isosceles trapezoids, wherein eachleaflet window side is defined by the window sides of the isoscelestrapezoid, and wherein each leaflet window base is defined by a baseelement.
 33. The method of forming a prosthetic heart valve of claim 30,wherein wrapping the film about the leaflet frame comprises wrapping afirst film about an inner surface of the leaflet frame and a second filmabout an outer surface of the leaflet frame, wherein the leaflets aredefined by the first film and the second film bonded together in theleaflet windows.